Unopposed estrogen therapy is contraindicated in which type of cancer?

Unopposed estrogen therapy is contraindicated in endometrial and estrogen receptor-positive breast cancer due to the stimulating effects of estrogen on these tissues. Estrogen promotes the growth of endometrial cells and can exacerbate the progression of endometrial cancer, which is particularly sensitive to hormonal changes. In estrogen receptor-positive breast cancers, the presence of estrogen can lead to increased cell proliferation and tumor growth, making unopposed estrogen a significant risk factor for worsening the condition.

In contexts of other cancers like lung, colon, or ovarian cancer, while these cancers may have their own specific treatment considerations and contraindications regarding different types of hormone therapies, they do not have the same direct contraindication regarding unopposed estrogen. The specific hormonal stimulation of the endometrium and hormone-sensitive breast cancers makes them unique in this respect, leading to the necessity of considering alternative therapies or the addition of progestins to mitigate these risks when estrogen is used.